1. Field of the Invention
The present invention relates to a vehicle headlamp and more particularly to a vehicle headlamp in which a power supply socket is attached to the discharge bulb that is used as a light source thereof.
2. Prior Art
A typical vehicle headlamp uses a discharge bulb as its light source. In such a vehicle headlamp, the discharge bulb is attached to a reflector, and a power supply socket (merely called a xe2x80x9csocketxe2x80x9d) is brought into an engagement with a base portion of the discharge bulb by rotation so that the socket is attached to the discharge bulb.
In this vehicle headlamp, if the rotation of the socket is incomplete or improper due to the reasons for, for example, lack of experience of an operator, the socket would fall, or a contact failure would occur to the terminals used in the headlamp.
For the purposes of solving such problems, one of known headlamps takes a unique structure. In this headlamp, a restriction wall is formed on a cover that closes an opening formed in the lamp body. This opening is used when, for instance, attaching a discharge bulb to a reflector which is installed inside the lamp body and when attaching a power supply socket to the discharge bulb. The restriction wall is formed so that it surrounds most of the side surface of a power supply socket when the cover is attached to the lamp body to close the openig. Thus, when the cover is attached to the lamp body in a state where the power supply socket is normally attached, and the opening is closed by the cover, then the restriction wall of the cover is engaged with the side surface of the power supply socket and prevents the power supply socket from rotating. As a result, unless the power supply socket is not rotated completely to a normal attachment position, the restriction wall interferes with the power supply socket, and the cover is not attached to the lamp body. On the other hand, if the power supply socket is rotated completely to the normal attachment position and is attached to the discharge bulb, and the cover is attached to the lamp body, then the power supply socket becomes incapable of rotating.
Accordingly, in the above headlamp, it is possible to avoid the connection between the discharge bulb and the power supply socket from being left incomplete. Also, falling of the socket due to the loosening of the power supply socket or a contact failure of the terminal after the power supply socket is attached normally to the discharge bulb can be avoided.
However, generally in a vehicle headlamp, it is necessary to tilt the reflector in order to adjust the irradiation axis (or to make an adjustment of the optical axis). In the vehicle headlamp designed so as to prevent the power supply socket from loosening by the restriction wall that is provided in the cover as described above, there is a possibility that the optical axis is not adjusted as expected because of the interference that occurs between the power supply socket and the restriction wall of the cover when the reflector is tilted. Another problem in such a vehicle headlamp is that, upon assembling, it is difficult to attach the cover to the lamp body smoothly since the restriction wall comes into contact with the power supply socket.
It is, therefore, an object of the present invention to provide a vehicle headlamp that avoids incomplete or improper attachment of a power supply socket to a discharge bulb.
It is another object of the present invention to provide a vehicle headlamp that avoids a fall of the power supply socket from the discharge bulb after the power supply socket is attached to the discharge bulb.
It is still another object of the present invention to provide a vehicle headlamp that avoids connection failure between the discharge bulb and the power supply socket.
It is a further object of the present invention to provide a vehicle headlamp that prevents hindrance to a tilting movement of the reflector to which the discharge bulb is attached.
In order to accomplish the above objects, in the vehicle headlamp according to the present invention, a bar-shaped protrusion portion is provided on a cover that closes an opening formed in the back of the lamp body, thus allowing the bar-shaped protrusion to come into contact with or to be positioned adjacent to a part of the power supply socket when the cover is attached to the lamp body, thus preventing the power supply socket from rotating.
With the above structure of the vehicle headlamp according to the present invention, the bar-shaped protrusion portion interferes with the power supply socket and thus disallows the cover to be attached to the lamp body unless the power supply socket is attached to the discharge bulb in a normal state. Therefore, an incomplete attachment of the power supply socket to the discharge bulb is avoided.
Further, once the power supply socket is attached to the discharge bulb in the normal state and the cover is attached to the lamp body, then the power supply socket is prevented from rotating by the bar-shaped protrusion portion of the cover. As a result, falling of the power supply socket due to loosening of the power supply socket or a connection failure between the discharge bulb and the power supply socket is avoided.
Moreover, the protrusion portion that is provided in the cover is a bar type, and it is not a wall type that contacts the most part of the side face of the power supply socket as seen in prior art headlamp. Therefore, the protrusion portion would not hinder the reflector from tilting.